1. The Field of the Invention
The present invention relates to interbody spinal fusion implants and, more specifically, to interbody spinal fusion implants having locking elements that outwardly displace for selectively locking bone screws.
2. The Relevant Technology
The spinal column is made up of spaced apart vertebra that are each separated by a cushioning disc. If a disc ruptures or is otherwise damaged, the adjacent vertebra can press against the spinal cord which can cause pain and loss of mobility. In one approach to treating a damaged disc, at least a portion of the damaged disc is removed and a spinal fusion implant is inserted between the adjacent vertebra. The implant keeps the vertebra separated to prevent the vertebra from pressing on the spinal cord. Eventually, the adjacent vertebra fuse together about the implant so as to preclude any movement between the vertebra.
To help fuse the vertebra together, the implant is formed with a hollow cavity that is manually filled with a bone growth material, such as bone allograft, prior to insertion between the vertebra. The openings on the implant enable the bone allograft to facilitate bone growth between the vertebra.
To help keep the implant properly positioned and stationary as the adjacent vertebra are fusing together, bone screws are passed through the implant and are screwed into the adjacent vertebra. One risk associated with using bone screws is that through movement of the patient, the bone screws can work loose and back out of the implant. The movement of the bone screws can cause the implant to become loose and prevent proper fusing between the vertebra. In addition, a loose bone screw is a risk to a patient as it can create obstructions or damage surrounding bone or tissue.
Various approaches have been used to help lock bone screws to spinal implants. Such approaches, however, have typically suffered from shortcomings such as being ineffective, difficult to use, or having a relatively high risk that all or a portion of the implant will dislodge. Accordingly, what is needed in the art are spinal implants having improved assemblies and methods for locking bone screws to the implants.